Smartphone shipments are likely to reach one billion mark worldwide for the first time this year, a new report has said.

According to analysts Deloitte, this would double the number of smartphones in use to two billion by the end of the year.

In a new report, the company said that although it expects to see shipments of one billion smartphones this year, around a fifth of smartphone owners are unlikely to use their phones to connect to the Internet.

According to the Telegraph, Deloitte said that smartphone ownership will increase this year in part because of "hand-me-down" phones given to friends or relatives by someone who upgrades to a newer model.

However, the company warns that these users may not be able to get the full benefit of owning a smartphone because older devices may be unable to cope with the latest apps or with more complex websites, the paper said.

Last month, industry analysts IDC predicted that smartphone shipments for 2012 would reach 717 million, which represents a 45 per cent increase on the year before.

According to the paper, smartphone shipments worldwide are led by South Korean mobile maker Samsung.